tr-uby



F. J. TRUBY.

AUTOMATIC TRUNKiNG SYSTEM.

APPLlCATiUN men mean 191e,

Reissued Nov. 15, 1921.

15, 28. 3 Si-lEI:TS---SHEEi 1.

UNITED STATES PATENT OFFECE,

IRANKLIN .T. TRUBY, ,OF CHICAGO, ILLINOIS, ASS IGNOR TO AUT'OMiKTIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A COBZPOR-ATION OF ILLINOIS.

iicrommrc rrwnxme SYSTEM.

15,228 Specification of Reissuezl Letters Patent. Reisgugfl Nay, 15, 1321,

Original No. 1,122,556, dated December 29, 1914, Serial No. 663,303, filed January 18, 1911. Application for reissue filed Angust 30, 1816. Serial No. 117,816.

To all whom it may concern: lhe object of myinvention is, therefore,

Be it known that I, FRANKLIN J. TRUBY, a the provision of an improved apparatus for 55 citizen of the United States of America, and and method of trunking which will not be resident of Chicago, Cook county, Illinois, open to any of the above objections, and have invented a certain new and useful Imwhich will give efficient trunking service provement in Automatic Trunking Systems, with a minimum wear and tear, and with of which the following is a specification. greater certainty of operation than hereto- 0 My invention relates to telephone exforechange systems 111 general, but more particu- To the foregoing and other useful ends I 10 larly to systems inwhich automatic trunkprovide a trunking apparatus in which only .ing switches are employed, and especially to one line switch operates when a subscriber systems in which a non-numerical trunking makes a call-that is to say, only one in the 65 switch is allotted to each subscriberstelegroup to which it belongs, and in which phone 1' P i t mv i ti th even this is often unnecessary, inasmuch as trunking switches, such as the aid ubeach switch is alwaysin electrical connecscribers line switches, have been operated tion with the trunk line which it last emvarious Ways F example thgsg ployed in extending the calhtherebymaking 7O switches have been constructed to operate on it possible for a subscriber to call again and the rotary principle. and provided with get the same trunlrline that he had for the means whereby they are always restored to previous Call, providing in the interim the normal position or starting point after each same has not been appropriated for use by call, In other cases these switches have some other subscriber, it being unnecessary, 75

- been so constructed and operated that the when this is possible, for the callingsubtrunk lines are selected ahead of the calls, scribers switch to rotate from one trunk each switch, while at rest, being; in selective line to another in an effort to iind one that relation to the next idle trunk line, so that is idle, as will hereinafter more fully appear. the first calling subscriber will get the pre: In the accompanying; drawings, Figures 1 80 selected trunk line. The first method has n 2 t k n toge her represent a complete been found to be objectionable for various circuit connection established between a call reason as for example if several trunks ing substation A and a called substation A, are busy it requires some time for the line in a system embodying the principles of my switch of the calling line to Find an idle invention. Fig. 1' shows a substation A. to 85 trunk, and during this operation the callin the line of which there is allotted a so-called subscriber may begin calling the number of rotary line switch G. The line switch C has the called subscriber by transmitting elecaccess to a number of trunk lines, each of trical impulses in the usual and well known which leads to a selector similar to the seway, in which event the call would not go lector switch shown at D. Fig. 2 represents so through in the proper manner. The second diagrammatically a connector E, rot ry lint method has also been found to be more or S tch 0' and Substation A. The switchC' 40 less, objectionable, in. my judgment, as each and substation A are similar in all-respkects time a subscriber calls he causes the actuato the line switch C and suhstation l of tion of all of the line switches of that g- At a battery is shown which is Q5 group-that is to say, all the switches that used for talking and operating purposes. are not in use-in order that another trunk The battery B has its positive terminalpret' may be selected for the next calling suberably grounded at G. At M a busy signalscriber. In other words, and with this secng ma. blue is represented and at R a ring-- 0nd method, each calling subscriber not only m current generator is shown. loo

ca-uses the actuation of his own switch, in ig. is a diagrammatic representation order to obtain connection with the preof the-mechanism .ot the switch C. bo'selected trunk line, but also oauses all of the 4; 1s' a mod1fied form of the subidle line switches of that group to move on SCIlb8rS individual sw tch.

from said line anl come to rest in selective The substations used in a system embodylee relation to somerother line. 7 ing the, principles of my invention may be hi ttWEtiEB my invention compi'iso at oobstation A tho i'ocoi'voi' 11, switch hook 3 trzmo mittot lfilltfgtitfi 5., oooticooei" ti, impulse gs it? it "whioh otc forced out of ehh it on tho impulsc Whcoi Jill is occoit it it to which them (to shown) poo it 'hoti tho switch ioioovoi of to FL) tho opiiogg i and into coit tho opting 7 whctohy tho hi'ihon, and. the mt iopi rings limo conhtitigcci oi om it iioti it in mrioo.

lino switch com gi'ioos among it tho tioohio-woomit i'oiay ii,

comprises it hot o' Ji' it. mcoho of oi ovor hooks oi.

"i ooi'isiot ott' tom. i,

;o col ectors ouch its the ".lihc hank ooiitoots of t multiplied as h it iitimhor of of switches ihoi of init iich form to tho soof the poo iohiol ooii- F o oititfiltifltti ooiooo ltllii tho Ctltlb ilooii ocgmoht if. ilizioh tho 'wipcro Q22, omit pt'oviiiotl with tl Wino, so that ttit mic ohm pocooo oii contact onothot' Willi onto one 3 l" how tho w t) itt'tti 53 5: on?) it by tho mogoct Mo tho mo 9h, rotchot to .i icioot tho 't ro iho tcototo tit, oml oooh aioo h itiioot. ii which it? coimoc it ioilcii by tho "vim- I"? fi'ltl'tl H1 @0111" i Tito pot-- the oiiio .omtch that it? in wo'vaio .iioonor, m qoo yh tho moctiom ot States Lcttci's Patent #815,1Tth gzgwmtotl March 13, 1906, to Koith, Erickson ltlwioio son. The connector, like the selector i), is; pi'oz idcti with the usual shaft carrying tho wipcrs 4.3, it and t5, tho voi'ticol motion of which shaft is COHiJlOiiQti by tho vcrti-izl magnet 46, and. the rotory motion by tho rotary magnet -17. It also comprisco tho oiotwacting relays i8 and it), clouhlo wound line reiay o0, rclcasc magnet 51 and private magnet :52, which latter controls o sido switch carrying the wipers 53L 5t, 55, 56 and .57, and in addition the connector is Frovided with a ringing i-elziy 58, hat-lo iritlgo roiay 59 and tho hosyiiooking icy tit). i

'A olozii'cr understanding of my img ii'ovctl so system may be obtained from @Hpiittttttion of the operation by whiolti oiio saith toi'ihor calls onothcix Assuming for oxohmic, that the suhscrihci" otsubstiitioo it dcoircs to coil the subscriber at sohototion. A, to which is aliottotl the iioc :itt'iittl, tho motto of operation is as follows: To call the immhor 2&0 the siihsciihci' iii;

Sit

substation it rcmovoo his receiver from. tho hook mini opcrotch his coiling clcvico onco, n the wcih known mamioit, for each digit. Tho iromovai of the I'cccivcr till the Fittbfillltttifll) A closes on energizing cii'coit tlmough tho law 18 ofthc switch C. This oircuit cw tonrls from ground G through the spi'ii 61 and 62 of the rchiy .tt thcncc throu o, the springs 13 and 6t tho ItEittj/ it, oondiictoi' 1.6,'spi'ingo and 1t, impiiioc opifihgs ii omit 8., roocivoi" Q iltitflliiitftlijiltilt' t, i Jitt fiiflt 15 65 cod tit), relay it timings 6? and i8 to 'tho hottoi'y iootltitl, thciico through hiittcr ii to wound ho i'chi y18 upononcig' mg, clout it circuit tcmliiio' from 'ogro .i. l G through tho springs 70 and Ti, whirling; T5 of tho relay 1?, theme through the springs 67' and 68 to hottci'y B. If the trunk ,upon which thc Wipers E82, -3 and 24; sttimiing is idio tho rcioy will attract its otmotuic, Whoi'ohy the omrih tit, 65 oiiol 98 oi oc-ihittocl out oi? (moo out with tho optiiig o #333, anti 99 mild into oiiggiigomomt with tho springs it, it) and 10 th rcooocti w, (i tho spring hjllt ohii'tod into o gagct. t with the spring "ttt oil o optioggo t anti tit'i jh .o it it) ciooco to time b t to this flilithfiflt Ii through tho wi on; i 524. li'iiotBototmiiog of tho iiiio ow to tho y 1 tot!) cfo relay 4:1. This circuit extends from ground G through the lower winding of the relay 4:1. side switch wiper 35, individual segment 76 of the bank 27, wiper 2 common seg- 5 meat 77, springs 78 and 6' 1, thence to and through the substation A, back over the conductor 15. through the springs 65 and 79, common segment of the bank 25, wiper 22, individual segment 80, wiper 34 and upper winding of the relay 41 to the battery lead 69. The relay 41, upon energizing, closes a circuit through the slow relay 4th This circuit extends from ground Gr through the springs 81 and 82 and the relay to to battery. The relay 40, upon energizing, puts a guarding ground potential on the private bank contact of the trunks leading to the selector D in the private banks of all of the individual switches that have access to the selector D. Thus, as soon as the relay 4O energizes there is (in this case) a ground potential on the contacts 83, 84:, etc. This guarding circuit extends from ground G through the springs 85 and 86 and the conductor 87 to the said private bank contacts. The energizing of the relay 4() also discon nects the impulse spring 88 from the release magnet 42, and connects the said impulse spring 88 through the relay to the vertical magnet.

' If the trunk upon which the wipers 22, 23 and 24 are standing had been in use .when the subscriber at substation A removed the receiver. there would have been a guarding 85 ground potential on the private bank contact. as described above, which would have caused the wipers to have been advanced off this trunk to an idle one. Upon the energization of the relay 18 a circuit would have been closed through the motor magnet 20 and winding 89 of the relay 1?. This circuit extends'from the ground at the private bank contact through the wiper 23, common segment of the bank 26. conductor 90,

springs 73 and 72 to the point 91. thence one branch leads through the winding H9 and springs (57 and (38 to battery. From the point 91 another branch extends through the interrupter springs 21, motor magnet 20,

5o thence through the springs 67 and (S8 to battery. The current in the winding 89 opposes the current in the winding 75, thereby holding the relay 1'? in a deenergized position,

in which position the trunk lines 92 and 93 65 are open at the springs 79 and 78. The motor magnet 21), when its circuit is closed, attracts its armature 94. The pulling up of the armature 94 breaks the circuit of its own magnet and also operates, through the mediuin ot' the pawl, 95 and ratchet wheel 96 (Fig. 3) to rotate the shaft 97 (upon which aresecured the wipers 22, 23 and 24) one notch. As soon as the wipers are moved one strip the wipe 23 leaves the groundedcon-.

taf't, breaking the circuit of the rotary mag- 101 and 102, winding net 20 and the winding F9 of the relay 1?, it the next trunk is idle. If, however. the next trunkis busy. the wiper 23 finds another grounded contact. causing the magnet 20 to again operate in a manner similar to that of a buzzer to rotate the wipers past the busy trunk to an idle one. Of course, as soon as the circuit of the winding 89 of the relay 17 is broken by the wiper 23 passing otl' the last guarded contact. the relay 1i operated by the current in. the winding in the same manner as explained when the wipers were resting on an idle tr..nk.

The shifting of the springs 13-1 and (3?) from engagement with the springs [53 and 6,6 and into engagement with the springs 78 and 79 breaks the circuit of the relay 18, which immediately falls back. The relay 17 being slightly slow acting holds up until. the relay 40 of the selector l) pulls up, whereby ground potential is placed on the spring T3 over a circuit hereinabove traced. As the relay 18 dci nergizes. a holding circuit for the relay 1? is established. said circuit extending from this ground poten tial through the springs 73 and 74, springs 7:) and springs (57 and 68 to battery. ()ne branch also extends through the springs and 98 to the private normal conductor leading to'the private bank contact of the calling line in the banks of all of the connectors that have access to said lines. whereby the calling line is prevented from being called after it has started to set up a connection.

The foregoing is the operation of the central oliice mechanism upon the removal of the receiver from the hook at the calling substation. The subscriber at substation A now operatcs'the calling device for the first" 105 digit of the desired number.' The teeth 9 on the impulse wheel 10 operate. during the backward rotation of said impulse wheel. to force the spring 8 out of engagement with the spring T, whereby the circuit through the relay 41 otthe selector D is broken twice. The relay al-deiinergizcs to close a circuit through the vertical magnet 31 in series with the relay This circuit extends from ground G through the springs H1 and 88, springs 103 and 104, slow relay 38, vertical magnet 31 and side switch wiper 36 to battery. The vertical magnet opeiates to raise the shaft and shaft wipers two steps to a point opposite the second levels of terminals of trunks leading to the connectors E. As soon as the vertical shatt is raised one or more steps the arm 111 allows the spring 112 to engage the spring 113, whereby one point inthe circuit of the 125.

release magnet 42 is closed. The relay 4.0 being slow acting-does not denergize during the momentary interruption of its energizing current by the disengagement of the springs 81 and 82. Also, the relay 38, which line at the substation A has been broken.

for the last time for the first digit, at which time the relay 38 deihiergmee end breaks the private magnet circuit. The private rho net, upon de nergihihg, allows the side switch wiper-e to pass to eecoird position, The shifting of the Wiper 36 trouilirst to second position shifts the battery CODHECP tion from the vertical to the rotery magnet. A circuit is now completed from ground G through the interrupter springs 108, rotary magnet 32, slow relay 39 and side switch. Wiper 36 to battery. The rotary 1m met energizes upon the closure of this circuit to rotete the shaft end wipers one and onto the first contact or": the second level, to press down the private magnet iii-mature end to break its own circuit at the iuterrupter eprings. The armature 109 foils back when the circuit of its magnet is broken. If the first contact is idle, the privote armature will also tell heel: end allow the side switch Wipers to peas to third posh tiou. If, however, the first Contact is busy, the private wiper 29 Will fluid the contact upon which it rests grounded in e manner which will he explained later, whereby e circuit is closed extending from said grourul at the private heel: contact through the private Wiper 29, conductor 110, side switch Wiper 87 {in second position) and private megnetfill to hottery. The private me let energizes end holds its; armature in am. open eted POSiijlOlL, thereby locking the side switch in the second poeitioo. The ro magnet ugeiri to rotate the m .X and shaft wipers to the next hank co: ct. lit the second trunk is idle, the side switch Wipers will he allowed to pass to third position. If, however, the second trunk is busy, the o jieretiooe above described will he re peated to rotate the wipers to the third contact, and so on until the private iper strikes the terminal of o non-busy trunk, ht which time the Side switch ui'ipere Will; pests, to the third position. The poeeiug ol the Wipere end 35 to the third position cone pletee the iine from the ceiling: e? "tritium to the connector E, thereby (dosing; (in energieing circuit through the relay 50 of the eeid connector? This circuit extends from ground (i through the lower winding of the relay 50, thence over the heavy conductors to and through the substation A end hitch over the heavy conductors, and through the the calling; device or the FPCUl'li'l. t

tact 1 epriiige lei" and 7 52:6, 1

{it of the coufiector (le hergrizee trvi tieel i'negghet 4h. c; exit eprn" go 1 l end 1354) puts it uooih heel-i on .he ehiiw relay ii) oi the end also puts giutrdii private .hiool: cimtects er in the lmiilre of ell oi the l'i-zive access to the coime tor I circuit extei'ide from e.

t? it sideswitchwiperUZ,eprm I conductor 123 to the choreuieut .v henlr coiitzicte The former oi. over the Same circuit to tl 3 i, theme throng v conductor "lilo, side so R I 1% end 1525 end reloy 4th to ht, ry I interval of time eliipsee, her ,ver, i' t the time the eide switch xvi th selectorpeee to the th "d tiu'ae it the yhovehic t tentlel is plum-ail on the teeter llhe relay 89 is er. i grouiid spring 127 for the m mg a guero potcifhi on tljie vete henh: contact until the g 'rouho plied from the tltirlfllmfl lfli. 'lhe which was energized in M h tar-y magnet, is slow ectir their h'miue iii in eher after the side switch, the third ooeitioii w. v on the 'orivete hutch co'otucte i euteiuiinp; from ground iith er, on private Wiper 539 to the (l i tact course it is evident thiit 39 must he eli-ghtl r tucker in its at the release relay 4:0, otherwise the would he releeeed.

The central oflice mechenieui .ie readiness to respond to the ope the callin device for the As the eullecriher ct euhetiitiou the line is fig f i'llhflllfiilfhl, tw in ecii'euit hroi th the verticel rum; seriee w. h the relay d8, the same are de scribed for the u'uiguet operates to raise the shuit and 5 Wipers two steps to El pi'ieition em'meitc t :v second level of herd: cohtocte. 'llhe slow rehiy lil dei nergizeri: ii moii'neut er the heat ii'upiilee hers been sent throu rh, and permits the private iueghet irl'iich wee one ed over a circuit extending from ground G through the springs 128 and 129 and magnet to battery, while the relay 48 was energized) to deiinergize, which in turn allows 5 the side switch wipers to pass to second position. The Wiper :36, in passing to the second position, shifts the battery connection from the vertical to the rotary magnet. The subscriber at substation A now operates the dial for the last digit 0. The line is opened ten times at the substation. The relay 5U deenergizes ten times to close the circuit of the rotary magnet 47 ten times. This circuit extends from ground Gr through the springs 114: and 116, 118 and 119, 1:30 and 131, magnet. 47, Wiper 56 and relay 48 to battery. The rotary magnet energizes and deenergizes ten times to rotate the shaft and shaft Wipers onto the contacts of the called line. The relay 48 does not deenergize until the last impulse has been transmitted. It then deenergizes and breaks the circuit of the private niagnet 52, which in turn falls back and allows the side switch wipers to pass to third position. The Wipers and 54, in passin to third posi tion, extend the conductors irom the calling line to the called substation A. The Wiper 55, in passing to third position, puts a guarding potential on the private bank contact of the called line in the banks of all of the connectors that have access to the called line. This guarding potential extends from ground G through the side switch wiper 5ft, springs 1.68 and 169 to the private Wiper 4d,; thence to the contacts above mentioned. A circuit also extends from this ground at the private bank contact through the springs 13:2 and 133 add cutofi' relay 134 to battery. The relay 134 energizes and disconnects both sides 01' the battery from the called. line at the switch C, thus making it impossible for the subscriber. at substation to call. While there is connection on his line. When the. Wiper 57 passes from second to third position it s-zhii'lts the holding groiuid from the release relay 40 of the selector D from ground G to grornd G through thesprings 11d and 5!} no. The wiper 56, in passing to third position. disconnects battery from the rate in quot urd r the circuitoi the ring r iy 58 circuit through the relap- 08 ext ads from ground G through the llltfil'l. r 135.75 and 137,

a relay 58, wiper '16 and ay 18 to battery. The rin ing relay F t-3 energizes and disconnects the calling from the called line, and manects'the ringing current 'enerator R with the called line. A ringing current then flows from one brush oi the generator 3 through the springs 138 and 139, side switch wiper 54, shaft Wiper 455, line eonductor 140, bells 1 11, condenser 142'. springs as M3 and 1%, line 1&5, wipers-i5 and 53 and springs 146 and 14 7 to the other brush of the generator R. The interrupcr in the ringer relay circuit allows the bells to be rung intermittently. Upon hearing the signal the subscriber at substation A. removcsthe receiver from the hook, which thereupon. or as soon thereafter as the ringer relay deenergizes, closes a circuit through the backbridge relay 59, thus supplying the called subscriber with talking battery current. This circuit extends from ground G through the lower winding of the relay 59, springs 14S and lit), wipers 53 and line 14-53, springs 14% and H9, impulse springs 150, receiver 151. transmitter 152, line 140, Wipers 13 and 54;, springs 139 and 153 and the upper Winding of the relay 59 to bat- -tery. The relay59 energizes over this circuit and operates to open the circuit of the ringer relay 58 at the springs 137111111 136. The subscribers at the two substations may now carry on an uninterrupted conversation until completed. The voice currents liow over the .heavy conductors shown in the drawings through the condensers 154 and The release of the central oflice mechanism is initiated by the hanging up of the receiver at the calling substation. The replacing of the receiver on the hook at the calling substation opens the line by the disengagement of the springs 12 and it. The relay 50 of the connector Fl falls back when the line is thus opened,- and opens the circuit of the relay 40 ot' the selector D and 00 relay 49 of the connector. "The relay 49 falls back, whereby a circuit is closed through the release magnet 51. This circuit extends from ground (i through the springs 114i and 116. 118 and 117, magnet :31 and off normal 05 springs 156 and 157 to battery. The switch mechanism is released upon the energization of the magnet, and the shaft, upon falling to its lowest position, again breaks the cir-. cult of the release magnet.

The lire ring of the holding circuit of the relay 4O 01 the selector D allows it to delincrgize and close the circuit of the release magnet 42. This circuit extends from ground G: through the springs 81 and 88, sprii'igs 103 and 105, off normal springs 112 and 113-3 and magnet 42- to battery. Litre the connector, the selector releases'upon the energization oi the magnet 42, and opens the cit normal spring contacts when the shaft reaches she lowest position. The relay 10, upon de'einergiaing, also removes the guarding ground from the banks of the in dividual switches and the holding ground from the relay 17, which falls back and again connects "the relay 18 to the battery. Thus the switches are put in readiness for another call.

It the called line had been busy when called from the substation A, the private Eli wiper 46 of the connector E would have found the contact upon which it was rotated grounded in ii manner hereinnbove ere phiincd. This ground on the private bank contact would have maintained an energyiz ing ircuit through the private magnet 52 in series with the relay 59 after the relay 48 deenergized upon the completion of the last set oi. impulses; This circuit extends from the grounded hank contact through the wiper 44h springs H59 and 168. lower winding of the relay 59, ringer reluysprings 148 and 146i, wi er 53 (in second position}. springs 16% m 12).) and private magnet 52 to hot teryw The relay 59 is energized over this circuit, while the private magnet 52 remains in the energized position in which it was placed by the relay 48. The simultaneous energinntion of these two relitys 59- and 52 closes an energizing circuit through the relay 60. This circuit extends from ground G through the springs 128 and 161, springs 162 and 163, relay and'springs 164 and 165 to catteryw The relay 60, upon energizing,

I opens the circuit ofthe rotary magnet and shifts the holding circuit of the magnet 52 and the relay 59 from ground at the private hnnk vcmitnct to ground G. Thisprevcnts the possibility of the side switch wipers passing;

to third position should the line become idle while the connector E is'stnnding on it. The energizntion of the relay 0 also supplies the ceiling subscriber with a busy signal extending from battery through the secondary of the machine M. springs 166 and 167, wiper 54h springs 139 and 153, thence through vthe condenser 154 over the heavy conductor to and through the snhstntion A, and back over the heavy conductor through the lower winding of the rela 50 to ground. Upon hearing the busy signal the subscriber at substation A. replaces the receiver on the hooh' which releases the switches in the same manner as shove described.

Having described the operation of one form of individnni switch employing; the principles of my invention, I'will not?" describe the modified form shown in Fig. 4. As shown in at, the modified form of the switch comprises, anion tetnhle shaft 1'75 carrying four wipers 176., Ni, 178 end 1T9, all insulated from eiich other and from the shaft 175. These Wipers are such provided'with three arms; so arranged that as one arm passes off the last contact, another arm will pass onto the first contact-m Electrical connections are made with the wipers through the medium of the hrnshes 180, 181, 182 and 183. The shaft 1% is rovided with a hub 184, which hubis provi ed with ratchet teeth through the me dinm of which the shaft may be rotated by the magnet 185 and its armature 186. The Incet 185 controls a second urmatu re 187 in comprises two windings 188 and 189,

min 1920 other details, a ro' through the flift'hit'lgs $155 and content.

When the winding; ind or" et-d it nttrnct-s the nri'nntnrc 1.871, hut in not strong; enough to opernte the erinntni-e 1%. The winding; 1%, operates hotlri :n'mntni'ns ihli and 187, his form of the switch is slso provided, with. n so-coiled side switi'zh com"- prising the arms iiild, 19% wi l 192? Mid thi which arms are curried on on mini 2% pin oted nt the point Qflfi. The side switch home are normally held in conti'ict with the oontnct points 195,19il, 197, 198 end 1951*, i'cspeotivciy against the tension of the spring 20"? h the tooth 208 on the arm 120th which cnojngres the end of the arm hilliu ii/"hen the nrnintnro til-7i is attracted by the min -net 1%, the min Z on which is attached sold. nrmnti down the arm hilt, tllfiililgfl ring; to e tooth 208 fromthe end oii the win nliii, nnd. allowing the side switch arms 11% to pi the cscapenuent tooth 208., .he ninggnct is quick to energize but slow to dehenci The proper operation of this nnignet inny he obtained by securing n ring;- oi copper around one end of the core. iimhiggn i if have represented the line coni'hictors iced. ing to the individual switch, nnd thetrnnli:

conductors lendingthercironi, the same no in Fig. i. For instance, the lii'ic wires and 16 are shown lending to the sidti switch arms and 191, respectively" The prii'i'ite nonnml conductor 211 lends to the side sw'i ,l'

The ti'nnh conductors nnd mo lend from the hnnh contacts on nnd in to the first selector Ehthc some no in i, The third trunli' condnctor 8i ll nds to tho first selector, just no in '1 hot instend of being connected to the o t in on the relay 40 it is connected to then: norninl spoiling 113, In fzhzt when the "form of liifiitlstilditl switch shown in t in need the wring? 86 and Boot the relay 4d nt'tiio first in zinc may be dispensed with. Tho wiper n the switch shownin. Fig. ien gnppee a fourth set of contacts which have no tii'nnh lino con nections, but one himpiy niniti "led with the lllti lliiii corresponding hohlis of oil tie individual switches which have scenes togroup of trunk lines. v I i t The operation of the switch in Fight ii is to; followsi When the coiling: snhscrihonhridgwg his tulhingcircoit across the line condncto'flsi 15 and '16, upon the removal oi? his cocci on from the switcl'i hoohin circuit chm through the winding i288 of the mngnot ifiti'ffifit This circuit from g i'icnnid G than some point 195. side switch Min 1%, line oondii tor 15, thence through the suhotntionfimni back over the conductor in side switch cm 13o 6 falls back and allows the springs 191, contact point 196, springs 217 and 218, 219 and 220 and winding 188 to battery B. The winding 188, upon energizing, attracts the armature 18?. If the trunk line upon which the wipers of the switch are resting at that time is idle. the operation of the armature 187 simply causes the side switch to pass from .fiist to second position. The movement of the side switch wipers 190 and 191- from first to second position disconnects the ground G and the winding 188 from the line conductors 15 and 16, and extends said conductors through the conduc tors 92 and 93 and wipers 176 and 177 to a. pair of trunk conductors 212 and 2-13 leading to a first selector. The side switch arm 192. in its operated position,- extends a guarding ground potential over the conducfor 211 to the connector private bank contacts of the calling line. The side switch arm 193, in its operated position. extends a guarding potential from ground G" through the contact point 203, arm 193. springs 236 and 224, interrupter springs 221 and 222. brush 183 and wiper 179 to the bank contact upon which it is resting. and -thence to the corresponding contact in the banks of all the individual switches in the group. The side switch arm 11%. in its operated position, connects the magnet 210 with the shaft wiper 178. and hence with the release trunk conductor 87 of the. particular trunk line seized. The calling subscriher may now extend his call through the selector and con nector switches in the manner previously described. If the wipers of the individual switch are standing on the contacts of a busy line when the receiver is removed from the switch hook, the wiper 179 is standing on a. grounded contact, which ground is'supplied through some other occupying switch in the manner explained above. In tuis case the attraction of the armature 187, upon the removal of the receiver, closes a circuit from the grounded contact upon which the wiper 179 is resting, throughthe brush 183, cpn' ductor' 223, springs 222 and 221, 224 and 225'and winding 189 to battery ll. The Winding 189, upon energizing, attracts the armature 186, which operates to rotate thee.

shaft 175 one step, to open the circuit of the winding 189 at the interrupter springs 221 and 222, and toclose a circuit from ground G through the springs 226 end'227 and slow magnet 210 to battery. The magnet 210, upon energizing, operates to disconnect the ground G and windin 188 from the line and to prevent. the si e switch from passing to second position. By proper adjustment of the springs 224 and 225, and 226 and 227, the circuit of the magnet 210 may be closed before the side switch has left its normal position. W hen the circuit of the winding 189 is broken. the armature 18(3 221 and switch in the same manner 210 denergizes and again connects the w1nd-' ing 188 to the line. The armature 187 is thereupon attracted and trips the side as when the wipers are standlng on the contacts of an idle trunk at the time the receiver is removed from the hook. During the time the armature 186 is operating to rotate the wipers to an idle trunk line, the winding 188 remains energized over a circuit extending from the grounded bank contacts of the busy trunks through the wiper 183, conduc tor, i223, springs 237 and 220 and winding 188 to battery. This energization of the Soon'atter the armature 186 Winding 188. causes the armature 187 to hold the springs 224 and 225 in contact. so that the circuit oi the winding 189 may be closed each time the interrupter springs 221 and 222 come into engagement as described. The energization of the winding 188 is not strong enough, to interfere with the operation of the armature 186.

\Vhen the calling subscriber hangs up his receiver upon the completion of the conversation. the selector and connector switches are released in the manner explained- Since the conductor 87 is connected to the spring 112 of the first selector. the magnet. 210 of the individual switch will heenergized in multiple with the release magnet 42 of the first selector over a circuit extending from ground G to the spring 112. as previously traced, and thence through the conductor 87 (Fig. 4), wiper 178. brush 182, contact arm 1574, contact point 204:.and magnet 210 to battery. The magnet 210, upon energize ing, forces the side switch of the individual switch baclr to its normal position, leaving the individual switch ready for use in'another call.

It will be seen that with my improved construction and mode of o oration eachsnbscribers line switch is :lvays in electrical connection with some one or the different lilO trunk lines leading therefrom. The connected trunk line, it will also be seen. is always the one last employed by the switch in extending a call. that one of the switches is in electrical connection with a trunk line over which conversation is being carried on between the callingand called subscribers. Insuch case the connected trunk line is of course, the one For example, suppose p rl by tho owltcli iiicxtcmliog tincotlici'. howl",

ammo ,tliotthc at ii-cot and that no talking moioiciincll tli.crcb Still, 11 coco, J; owitcl'i its in clcotcicol i 011 Wl'ltl'l ooc of trimli: liiics, coil ,filfifil'il liiiiiili lino lo tho oioc which H'lilllfil'l ill cictcml l ovcri olily, tlicrc- I V is ooifiimlly linil limos coimcc cil "with o, ironic lino the one lost cmployctl lily it in ex Tho oi cli tliiic contcolloil ll is oi" cl'mfroc it in tlic conic iliifcctioii, Fltlltli iiih point oi" nomiol poci iozi. cci'iiiiins clicli timo iii concoction "ilfllllli lino mt Woo ciifiploycil. in tlic coll. ll? in tho i. tci'im that limo loccii. oppi'opi'iotctl by sonic Giflllll, tliczi wlicn tiic firot silliii colic tho switch will otlmmcc otcp mommy to automatically so- "lllllnlll lino. is possilllcfiiom mi cricliocgc oi" "niccci on the prin- ()Wl'l 21ml tlcscii for time siiiiloscrio til tho-mt tho occcooity F" lino a itc" in o woollyc oily ci'cnt, marl 'Wlicii Elli I ooc limo switch will QVill? to final oootloci itli Zlllllli 'for the :"s'witcl'i to in any tlic otlici switclioo of tlic some; will llilil tom is i'ciiiicccl to ho ccitoiiity of iiipcmtioo is M lly; as tho clonygci of o siiliocirilici" licgiiming' to sclicl in coll tlio lino itch lino c lil'ul'llfl to first sclcctoz" is; procto o, iiiinixmim,

' invcotioo is:

ii in o tclcplionc i-m o line, a now 11cc Witch tllllllll for 4 lcmliopg lilllflli'fll lfllll Sillil liiic Wily om mir'i'ioolly in clcco1: l'l'lfil'lt with. oiic ol sz'iicl twink nominally open. connections lictwccn llillIl lino Wipers, mow lowing o windings, 111021115; for one icing" oiic to cncicgizc soi -l relay to lly open concoctions when o lo moilc witl'i on itllc tmmlt, oocl 4o com-grim both of s to pi c'v'cct ooitl mloy from mllfil'liillllllf licli said wi'pcio contact with o lmiy truck. I

Lil ll ll ll ll" it tolcgiilioiio oyotcm sulioccilicfs no :i'ocpoiioiyc to such potcoiiol for m mo potential on its test conductor, a cut-off relay opcmlilc only when said line is calling, means for energizing sold cutoff relay as soon as on icllc trunk is found,' and means controlled by the cnergizotion of Fifllil cut-oil? relay to open the limo relay cimuit and conncct tlic lino with the line wipers of sold SWllillllL .lic o telephone system, a suloscrilicrs lino, a, trunk selecting switch individual tlici'cto lino wipers for soil switch normally tlisconncctcnl from said line, a line relay therefor, a plurality of trunks associated with Sltld switch, a test conductor or each trunk, automatic means formpplying a potcntiol to said. test conductors, means rcsponsivc to such potential for moving said switch progccssiyely over will trunks until lino and line Wipers only when the switch molics a call.

l. loo telephone system, a subscrlbcrs line, a trunk-col ecting switch imlwuioal tlicrcto, lino relay tllfllE'FOlB, lino ivipci'o lioi" soul switch normally disconnected from ti 1c lino, a 'gillurality of trunks associated with said switch, a test comluctor for can-ll trio-alt, lli'ltfllflflllifl means for applying a. p01 tciitial to said test conductors, moons responoivc to such otcntial for moving said switch progrcsswoly over said twinks until it ti'imltio found Without such potential on its tcst coiicliictor and a relay in said switch for both opening the line l'filly circuit and. for connecting the line am'l lino Wipers only when tlic switch. molrcs a coil.

5. in o tolcplionc system, a subscribors lino, on. automatic trunk-selecting switch in cliizicloal tlicrcto, o lino 'clny therefor contrololilo over two sides of Sllll line, in scrics, plurality of trunks associated with said switch, o tcst conduct-o1? for each trunk, automate, means for applying a potential to cold test co11rluctors,mcoos rcsponsivo to such potential for moving said switch pro grcsoivcly over said trunks until a trunk is found without cuch'potontiol on its test con cloctor, a cut-oil relay, means for energizing iifltlfl CHt Ofi relay only when sold line is coiling, and means controlled by the enci'gimtion of said cut-olf relay to open the lino rcloy circuit and connect the line with tho lino wipers of soil-switch.

(l. lfn it telephonic system, a siilocci'ibors lino, on automatic trunk-collecting switch intlivililiiol thoroto, lino Wipers for said switch i'ioc oolly (liocomicctcd from said line at tho v .iootiollolilc ovor two cities of said line in calico, o plurality of trunks associated of only one relay, a line rclay them:

' with said switch, a test conductor for each trunk. automatic means for applying a potential to said test conductor, means re sponsive to such potential for moving said switch progressively over said trunlrs until a trunk is found without such potential on its test conductor, a cut-off relay, and means controlled by said cutoff relay opening the line relay circuit and for connecting the line and line wipers when the switch makes a call.

7. In a telephone system, a suhscrihers line, an automatic trunk selecting switch individual thereto controllable over two sides of said line'in series, line wipers for said switch normally disconnected from the line at the springs of only one relay, a plurality of trunks associated with said switch, a test conductor for each trunk, automatic means for applying a potential to said test con ductors, means responsive to such potential for moving said switch progressively over said trunks until a trunk is found without such potential on its test conductor, and a relay in said switch for both opening the line relay circuit and for connecting the line and line wipers when the switch makes a call.

8. In a telephone system, a suhscribers line, i a trunk selecting switch individual thereto, a line relay therefor controllable over two sides of said line in series, a plurality of trunks associated with said switch, a test conductor for each trunk, automatic means for applying a potential to said test conductors, means responsive to such poten tial for moving said switch progressively over said trunks until a trunk is found without such potential on its test conductor, a single normally open connection between said line and each line wiper, a. cutoff relay, means for energizing said out-oif relay, and means controlled by the cnergization of said cut-off relay to open the line relay circuit and connect the line with the line wipers of said switch.

9. In a telephone system, a subscribers line, a trunk selecting switch individual thereto, line wipers for said switch normally disconnected from said line at the springs of only one relay, a line relay therefor controllable over two sides, of said line in series, a plurality of trunks associated with said switch, a testconductor for each trunk, automatic means for applying a potential to said test conductors, means responsive to such potential for moi lug said switch pro grcssively over said trunks until a trunk is found without such potential on its test conductor, a cut-off relay, and means controlled by said cut-off relay for opening the line relay circuit and for connecting the line and line wipers when the switch makes a call.

10. In a telephone systc sufiiscriher s line, a trunk selecting s iJ'Ol'l individual thereto controllable over two sides of said line in series, line wipers for said switch normally disconnected from the line, a plurality of trunks associated with said switch,

a test conductor for each trunk, automatic means for supplying a potential to said test conductors, means responsive to such poten-- tial for moving saidiswitch progressivey over said trunks until :r trunlr r; found. without such potential on its test conductor, and a relay in said switch for both opening the line relay circuit and for connecting the line and line wipers only when the switch makes a-call.

11. In a telephone system, a subscribers line, non-numerical trunk-selecting switch individual thereto, a normally open connection between said line and each line wiper, a line relay therefor, a cut-off relay, means for energizing said cutoff relay, means controlled by the energization of said cut-oil relay to open the line relay circuit and connect the line with the line wipers of said switch, and trunk lines associated with the switch, the wipers of said switch nor mally engaging one of said trunk lines.

12. In a telephone system, a subscribefis line, a non-numerical trunlrsclecting switch individual thereto, line wipers for said switch normally disconnected from said line at the springs of only one relay, a line relay therefor, a cut-off relay, means controlled by said cut-off relay for opening the line relay circuit and for connecting the line and line wipers when the switcli'makes a call, and trunk lines associated with. the switch, the wipers of said switch normally engaging one of said trunk lines.

13. In a telephone system, a suhscribers line, a non-numerical trunk-selecting switch individual thereto, line wipers for said switch normally disconnected from the line, a relay in said switch for both. opening the line relay circuit and for connecting the line and. line wipers only when the switch makes a call, and trunk lines associated with the switch, the wipers of said switch normally engaging one of said trunk lines.

1st. In a telephone system, a subscribers line, an automatic trunk selecting switch individual thereto, a line relay therefor controllable over two sides of said line in series, a single normally open connection between said line and each line wiper, a cutoff relay, means for energizing said cut-off relay, means controlled by the energization of said cutoff relay to open the line relay circuit and connect the line with the line wipers of said switch, and trunk lines associated with the switch, the wipers of said switch normally engaging one of said trunk lines.

a l ii lili in corics, ii cut-oil relay, I'HQHHS controlled iii. in u iclcpliiiiiio Sfffilfllll, ll subscribers lino, am :iuioiiiuiic trunk scli-ciix'ur swiicli i11- d'ii'i'luiil ilicrcio, liiic wipers for said H'Wlli'li li'lfilll'lllll}; ilisimiimwlcil from said line at the cg irings of only mic rcluy. :1 lion: rcliiy thoroiior coiiirollulilc mzcr two sidcu oi said lino by cold cut-oil r'cluy for owning); the limo rcr circuit and for couuociiii g me line :iiid .iic wipcic wlicn lino switch imritcs it call, ll ironic liiics liEiSz'lQllilllLl ii'illi iluc swiicli, il'ic wipcrs of fluid swilclr normally ciigziging oiuc of :iiiiii truck docs,

id, liii u iclcp" .iic oyctcui, siilrscrilucr s line, on iiu'loumiic truiiii 'iclcciing switch individual ilicrcio conirolliihlc over two sides sold lino io scrics, lino wipcrs for suid cw'lirli i'ioruuiliy diccitmncclcd from the line ilic springs oi. only one rcluy, said rcloy liotli opcning; ilio lino rcliiy circuit and coniicciii'ig' llic lino and lino wipers when the swiicli miilrcs call, and trunk lines associ'iiicd 'Wl'ill'l ilic switch, i'iic WlITiBIS of said swiicl'i rioriruilly engaging onc of said trunk liiios.

il in u liclcplionc system, subscribofls lino, ii cori-oiimcriccl trunk selecting switch ijiluiiliyildual llicrcfio, u lii'ic rcliiy lhcic'l'or cor irolliil'ilc ovci two sides ofsuid lino in series,

ll. sing-lo ruirmclly open (EUHHB' .ico lio'cwccii i'iiiid liuc and each iiuc wipcr, o ciuimfi rclcy, mo for cncrgiziug said cutoff rclay, u'iciiiis coiiirollcd by the cucryiriiiicu of, said culwoilf rcl iy to open tlic iiiic rcioy circuit cud, coiuiccc ilic lino wi'lxli tliic lino wipcro o. mid switch, and trunk liucu 'iihfilOClillififll' wi'lili l:- c swilgcli, tho i"- ors oi sz id switch ou l y cog-a ing oric sold truck liocii.

i ii iclcplionc sysicm, a siiliocrilacrls lino, Iiou-iniumcricul trunk sclcciiiig swilacl'i iridivii ml i licrcto, liiic wipers for cold 'swliicli, ii oinglc normally opcri concoction lociiwocii said lino cud ouch lino "wiper, u lmc rcliiy clicrcfor controllable ovcr two sidcc oi ocid lino iii scrics, o outcll' rclcy, moons co1ulrollcd by cold cut-oil rcluy for opening clic lino relay circuit and glor connecting the limo and lim wi' pcrs when. the switch 2i call, cud. i-ruiflincs associuccd with the si'viich, lilic wipcrs of mid switch normcdly engaging W of suid. 'iruulr lines;

, lilil a, iolcplionc system, u subscrilicrs Iiou-nunicriciil trunk sclcctiug switch i *iiucl illicrcfuo cou'trcllzililc ovcr two o c o iuu line in ucrics, lino wipers for said u iiicu normally discoiiiioctcd. from the lino lic i, of only ciao :i'cliiy in tlic switch,

' i rcluy lo iili cpcning the line rcliiycircuii; closing said uorruclly o pcn contuc s i 'ilic switch muliics i cull, cud truck limos, Wild. with film SWllJCli, tlio wipers of normally mic oi? sold i o, iclcpliciio limo, liriuiu sclcc individual thereto, a line rcluy therefor controlled over two sides of said line in series, a out off relay, said relay energized only Wl'lfili'L thc liuc is called, moons controlled by the cncrgizutiou of said cut oil relay to open circuit of the said lino relay, trunk lines loading from said switch forextcnding a coll, wipers for the said switch always in cugugcmcnt with one of said trunk lines, said couucctcd trunk line if idlc, always the onc employed by said switch in making a call.

21 In o, telephone systcin, an automatic switch, means for operating said switch to csiziiblisli a talking circuit, a relay for controlling tlic operation of said switch, a pair of windings for said relay, moans for closing ii circuit through both of Said windings in multiple to start the operation of said switch, and means for opening the circuit of one of said windings to stop the operation of said co criorgice said relay when an idle trunk line is reached to stop the operation of said switch.

23. In a telephone system, an automatic switch, moans for operating said switch to cstziblioli 1 talking circuit, :i relay for con trolling: the operation of said switch, a pair of windings for said relay, mcims for closliig u circuit through botlii' of said windings iii multiple to start the: operation of said switch, and means for opening the circuit of one of said windings to energize said relay to thereby stop the operation of said switch.

33-1. In u tclcphonc system, a line, a noniiumcricul trunk scl octing switch individual thereto, trunk lincs loading therefrom, said switch l'iaving lino wipers, always in electrical engagement with some 'ono of said trunk lines, said, connected trunk line i dlc, always the one cmploycd by tho said sw l ch in muliziug u c" ll, normally open connections-"be l wcen sold line and line wipers, a double wound relay for said switch, means forclosing a circuit' of both windings in multiple to stark said switch to rotate to select all-- oilicr of said trunk lines if said first trunk lino is busy, and mcano for opening the circoil; of one of said windings to stop the rotulaioii. of said switch and close said normally opcn connections. v V

25. 3111' a telephone system, a line, a nonnumerical switch for cxtcuding a. connection fi o said line, a lino roluy for said switch to'operate the switch, Wipers for said switch always in electrical engagement withsulne one of said trunk lines, said connected trunk lineif idle, always the one employed by said switch in extending a wall, ormally open connections. between said line and line wipers a relil'y for'olosing said normally open connections, means Ior eausing said switch to automatic-idly select an idle one of said trunk lines; a cut oil' relay for said 10 switch energized only when the line is called and operating to open the line relay circuit.

Signed by 1:10 at Chicago, Cook county, Illinois, this 25th clay of August, 1916.

FRANKLIN J. TRUB'Y. 

